STUDIES ON INITIATION AND DEVELOPMENT OF THE PARTNER ASSOCIATION IN GEOSIPHON PYRIFORME (KUTZ) V WETTSTEIN, A UNIQUE ENDOCYTOBIOTIC SYSTEM OF A FUNGUS (GLOMALES) AND THE CYANOBACTERIUM NOSTOC-PUNCTIFORME (KUTZ) HARIOT
D. Mollenhauer et al., STUDIES ON INITIATION AND DEVELOPMENT OF THE PARTNER ASSOCIATION IN GEOSIPHON PYRIFORME (KUTZ) V WETTSTEIN, A UNIQUE ENDOCYTOBIOTIC SYSTEM OF A FUNGUS (GLOMALES) AND THE CYANOBACTERIUM NOSTOC-PUNCTIFORME (KUTZ) HARIOT, Protoplasma, 193(1-4), 1996, pp. 3-9
Phagocytosis of Nostoc filaments by Geosiphon, a fungus closely relate
d to AM forming Glomales, was observed under light microscopes. Incorp
oration can only be performed if Nostoc primordia come into contact wi
th growing hyphal rips of the fungus. The fungal wall just below the a
pex softens, and fungal cytoplasm is bulged out repeatedly covering th
e vegetative Nostoc cells but not the heterocytes. New heterocytes are
differentiated by the internalised filament whose cells can increase
up to ten times in volume after recovering from incorporation strain.
The Nostoc cells are coated stepwise by short finger-shaped protuberan
ces of the fungal hypha. These hernia-like outgrowths first remain sep
arated, after 1 to 2 days they merge. Adjacent hyphal walls inside the
complex covering disintegrate. Periphal fungal wall portions are unit
ed to form a smooth strong outer envelope. Internalisation is categori
sed as phagocytosis. The partnership is partly specific, Nostoc strain
s capable of living endocytobiotically are often partners in other sym
bioses besides Geosiphon.